// Emacs style mode select	 -*- C++ -*-
//-----------------------------------------------------------------------------
//
// $Id:$
//
// Copyright (C) 1993-1996 by id Software, Inc.
//
// This source is available for distribution and/or modification
// only under the terms of the DOOM Source Code License as
// published by id Software. All rights reserved.
//
// The source is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// FITNESS FOR A PARTICULAR PURPOSE. See the DOOM Source Code License
// for more details.
//
// $Log:$
//
// DESCRIPTION:
//		All the clipping: columns, horizontal spans, sky columns.
//
//-----------------------------------------------------------------------------


static const char
rcsid[] = "$Id: r_segs.c,v 1.3 1997/01/29 20:10:19 b1 Exp $";





#include <stdlib.h>

#include "i_system.h"

#include "doomdef.h"
#include "doomstat.h"

#include "r_local.h"
#include "r_sky.h"


// OPTIMIZE: closed two sided lines as single sided

// True if any of the segs textures might be visible.
boolean			segtextured;

// False if the back side is the same plane.
boolean			markfloor;
boolean			markceiling;

boolean			maskedtexture;
int				toptexture;
int				bottomtexture;
int				midtexture;


angle_t			rw_normalangle;
// angle to line origin
int				rw_angle1;

//
// regular wall
//
int				rw_x;
int				rw_stopx;
angle_t			rw_centerangle;
fixed_t			rw_offset;
fixed_t			rw_distance;
fixed_t			rw_scale;
fixed_t			rw_scalestep;
fixed_t			rw_midtexturemid;
fixed_t			rw_toptexturemid;
fixed_t			rw_bottomtexturemid;

int				worldtop;
int				worldbottom;
int				worldhigh;
int				worldlow;

fixed_t			pixhigh;
fixed_t			pixlow;
fixed_t			pixhighstep;
fixed_t			pixlowstep;

fixed_t			topfrac;
fixed_t			topstep;

fixed_t			bottomfrac;
fixed_t			bottomstep;


lighttable_t**	walllights;

short*			maskedtexturecol;



//
// R_RenderMaskedSegRange
//
void
R_RenderMaskedSegRange
( drawseg_t*	ds,
  int			x1,
  int			x2 )
{
    unsigned	index;
    column_t*	col;
    int			lightnum;
    int			texnum;

    // Calculate light table.
    // Use different light tables
    //	 for horizontal / vertical / diagonal. Diagonal?
    // OPTIMIZE: get rid of LIGHTSEGSHIFT globally
    curline = ds->curline;
    frontsector = curline->frontsector;
    backsector = curline->backsector;
    texnum = texturetranslation[curline->sidedef->midtexture];

    lightnum = (frontsector->lightlevel >> LIGHTSEGSHIFT)+extralight;

    if (curline->v1->y == curline->v2->y)
        lightnum--;
    else if (curline->v1->x == curline->v2->x)
        lightnum++;

    if (lightnum < 0)
        walllights = scalelight[0];
    else if (lightnum >= LIGHTLEVELS)
        walllights = scalelight[LIGHTLEVELS-1];
    else
        walllights = scalelight[lightnum];

    maskedtexturecol = ds->maskedtexturecol;

    rw_scalestep = ds->scalestep;
    spryscale = ds->scale1 + (x1 - ds->x1)*rw_scalestep;
    mfloorclip = ds->sprbottomclip;
    mceilingclip = ds->sprtopclip;

    // find positioning
    if (curline->linedef->flags & ML_DONTPEGBOTTOM)
    {
        dc_texturemid = frontsector->floorheight > backsector->floorheight
                        ? frontsector->floorheight : backsector->floorheight;
        dc_texturemid = dc_texturemid + textureheight[texnum] - viewz;
    }
    else
    {
        dc_texturemid =frontsector->ceilingheight<backsector->ceilingheight
                       ? frontsector->ceilingheight : backsector->ceilingheight;
        dc_texturemid = dc_texturemid - viewz;
    }
    dc_texturemid += curline->sidedef->rowoffset;

    if (fixedcolormap)
        dc_colormap = fixedcolormap;

    // draw the columns
    for (dc_x = x1 ; dc_x <= x2 ; dc_x++)
    {
        // calculate lighting
        if (maskedtexturecol[dc_x] != MAXSHORT)
        {
            if (!fixedcolormap)
            {
                index = spryscale>>LIGHTSCALESHIFT;

                if (index >=  MAXLIGHTSCALE )
                    index = MAXLIGHTSCALE-1;

                dc_colormap = walllights[index];
            }

            sprtopscreen = centeryfrac - FixedMul(dc_texturemid, spryscale);
            dc_iscale = 0xffffffffu / (unsigned)spryscale;

            // draw the texture
            col = (column_t *)(
                      (byte *)R_GetColumn(texnum,maskedtexturecol[dc_x]) -3);

            R_DrawMaskedColumn (col);
            maskedtexturecol[dc_x] = MAXSHORT;
        }
        spryscale += rw_scalestep;
    }

}




//
// R_RenderSegLoop
// Draws zero, one, or two textures (and possibly a masked
//	texture) for walls.
// Can draw or mark the starting pixel of floor and ceiling
//	textures.
// CALLED: CORE LOOPING ROUTINE.
//
#define HEIGHTBITS				12
#define HEIGHTUNIT				(1<<HEIGHTBITS)

void R_RenderSegLoop (void)
{
    angle_t				angle;
    unsigned			index;
    int					yl;
    int					yh;
    int					mid;
    fixed_t				texturecolumn;
    int					top;
    int					bottom;

    //texturecolumn = 0;								// shut up compiler warning

    for ( ; rw_x < rw_stopx ; rw_x++)
    {
        // mark floor / ceiling areas
        yl = (topfrac+HEIGHTUNIT-1)>>HEIGHTBITS;

        // no space above wall?
        if (yl < ceilingclip[rw_x]+1)
            yl = ceilingclip[rw_x]+1;

        if (markceiling)
        {
            top = ceilingclip[rw_x]+1;
            bottom = yl-1;

            if (bottom >= floorclip[rw_x])
                bottom = floorclip[rw_x]-1;

            if (top <= bottom)
            {
                ceilingplane->top[rw_x] = top;
                ceilingplane->bottom[rw_x] = bottom;
            }
        }

        yh = bottomfrac>>HEIGHTBITS;

        if (yh >= floorclip[rw_x])
            yh = floorclip[rw_x]-1;

        if (markfloor)
        {
            top = yh+1;
            bottom = floorclip[rw_x]-1;
            if (top <= ceilingclip[rw_x])
                top = ceilingclip[rw_x]+1;
            if (top <= bottom)
            {
                floorplane->top[rw_x] = top;
                floorplane->bottom[rw_x] = bottom;
            }
        }

        // texturecolumn and lighting are independent of wall tiers
        if (segtextured)
        {
            // calculate texture offset
            angle = (rw_centerangle + xtoviewangle[rw_x])>>ANGLETOFINESHIFT;
            texturecolumn = rw_offset-FixedMul(finetangent[angle],rw_distance);
            texturecolumn >>= FRACBITS;
            // calculate lighting
            index = rw_scale>>LIGHTSCALESHIFT;

            if (index >=  MAXLIGHTSCALE )
                index = MAXLIGHTSCALE-1;

            dc_colormap = walllights[index];
            dc_x = rw_x;
            dc_iscale = 0xffffffffu / (unsigned)rw_scale;
        }

        // draw the wall tiers
        if (midtexture)
        {
            // single sided line
            dc_yl = yl;
            dc_yh = yh;
            dc_texturemid = rw_midtexturemid;
            dc_source = R_GetColumn(midtexture,texturecolumn);
            colfunc ();
            ceilingclip[rw_x] = viewheight;
            floorclip[rw_x] = -1;
        }
        else
        {
            // two sided line
            if (toptexture)
            {
                // top wall
                mid = pixhigh>>HEIGHTBITS;
                pixhigh += pixhighstep;

                if (mid >= floorclip[rw_x])
                    mid = floorclip[rw_x]-1;

                if (mid >= yl)
                {
                    dc_yl = yl;
                    dc_yh = mid;
                    dc_texturemid = rw_toptexturemid;
                    dc_source = R_GetColumn(toptexture,texturecolumn);
                    colfunc ();
                    ceilingclip[rw_x] = mid;
                }
                else
                    ceilingclip[rw_x] = yl-1;
            }
            else
            {
                // no top wall
                if (markceiling)
                    ceilingclip[rw_x] = yl-1;
            }

            if (bottomtexture)
            {
                // bottom wall
                mid = (pixlow+HEIGHTUNIT-1)>>HEIGHTBITS;
                pixlow += pixlowstep;

                // no space above wall?
                if (mid <= ceilingclip[rw_x])
                    mid = ceilingclip[rw_x]+1;

                if (mid <= yh)
                {
                    dc_yl = mid;
                    dc_yh = yh;
                    dc_texturemid = rw_bottomtexturemid;
                    dc_source = R_GetColumn(bottomtexture,
                                            texturecolumn);
                    colfunc ();
                    floorclip[rw_x] = mid;
                }
                else
                    floorclip[rw_x] = yh+1;
            }
            else
            {
                // no bottom wall
                if (markfloor)
                    floorclip[rw_x] = yh+1;
            }

            if (maskedtexture)
            {
                // save texturecol
                //	for backdrawing of masked mid texture
                maskedtexturecol[rw_x] = texturecolumn;
            }
        }

        rw_scale += rw_scalestep;
        topfrac += topstep;
        bottomfrac += bottomstep;
    }
}




//
// R_StoreWallRange
// A wall segment will be drawn
//	between start and stop pixels (inclusive).
//
void
R_StoreWallRange
( int	start,
  int	stop )
{
    fixed_t				hyp;
    fixed_t				sineval;
    angle_t				distangle, offsetangle;
    fixed_t				vtop;
    int					lightnum;

    // don't overflow and crash
    if (ds_p == &drawsegs[MAXDRAWSEGS])
        return;

#ifdef RANGECHECK
    if (start >=viewwidth || start > stop)
        I_Error ("Bad R_RenderWallRange: %i to %i", start , stop);
#endif

    sidedef = curline->sidedef;
    linedef = curline->linedef;

    // mark the segment as visible for auto map
    linedef->flags |= ML_MAPPED;

    // calculate rw_distance for scale calculation
    rw_normalangle = curline->angle + ANG90;
    offsetangle = abs(rw_normalangle-rw_angle1);

    if (offsetangle > ANG90)
        offsetangle = ANG90;

    distangle = ANG90 - offsetangle;
    hyp = R_PointToDist (curline->v1->x, curline->v1->y);
    sineval = finesine[distangle>>ANGLETOFINESHIFT];
    rw_distance = FixedMul (hyp, sineval);


    ds_p->x1 = rw_x = start;
    ds_p->x2 = stop;
    ds_p->curline = curline;
    rw_stopx = stop+1;

    // calculate scale at both ends and step
    ds_p->scale1 = rw_scale =
                       R_ScaleFromGlobalAngle (viewangle + xtoviewangle[start]);

    if (stop > start )
    {
        ds_p->scale2 = R_ScaleFromGlobalAngle (viewangle + xtoviewangle[stop]);
        ds_p->scalestep = rw_scalestep =
                              (ds_p->scale2 - rw_scale) / (stop-start);
    }
    else
    {
        // UNUSED: try to fix the stretched line bug
#if 0
        if (rw_distance < FRACUNIT/2)
        {
            fixed_t				trx,try;
            fixed_t				gxt,gyt;

            trx = curline->v1->x - viewx;
            try = curline->v1->y - viewy;

            gxt = FixedMul(trx,viewcos);
            gyt = -FixedMul(try,viewsin);
            ds_p->scale1 = FixedDiv(projection, gxt-gyt)<<detailshift;
        }
#endif
        ds_p->scale2 = ds_p->scale1;
    }

    // calculate texture boundaries
    //	and decide if floor / ceiling marks are needed
    worldtop = frontsector->ceilingheight - viewz;
    worldbottom = frontsector->floorheight - viewz;

    midtexture = toptexture = bottomtexture = maskedtexture = 0;
    ds_p->maskedtexturecol = NULL;

    if (!backsector)
    {
        // single sided line
        midtexture = texturetranslation[sidedef->midtexture];
        // a single sided line is terminal, so it must mark ends
        markfloor = markceiling = true;
        if (linedef->flags & ML_DONTPEGBOTTOM)
        {
            vtop = frontsector->floorheight +
                   textureheight[sidedef->midtexture];
            // bottom of texture at bottom
            rw_midtexturemid = vtop - viewz;
        }
        else
        {
            // top of texture at top
            rw_midtexturemid = worldtop;
        }
        rw_midtexturemid += sidedef->rowoffset;

        ds_p->silhouette = SIL_BOTH;
        ds_p->sprtopclip = screenheightarray;
        ds_p->sprbottomclip = negonearray;
        ds_p->bsilheight = MAXINT;
        ds_p->tsilheight = MININT;
    }
    else
    {
        // two sided line
        ds_p->sprtopclip = ds_p->sprbottomclip = NULL;
        ds_p->silhouette = 0;

        if (frontsector->floorheight > backsector->floorheight)
        {
            ds_p->silhouette = SIL_BOTTOM;
            ds_p->bsilheight = frontsector->floorheight;
        }
        else if (backsector->floorheight > viewz)
        {
            ds_p->silhouette = SIL_BOTTOM;
            ds_p->bsilheight = MAXINT;
            // ds_p->sprbottomclip = negonearray;
        }

        if (frontsector->ceilingheight < backsector->ceilingheight)
        {
            ds_p->silhouette |= SIL_TOP;
            ds_p->tsilheight = frontsector->ceilingheight;
        }
        else if (backsector->ceilingheight < viewz)
        {
            ds_p->silhouette |= SIL_TOP;
            ds_p->tsilheight = MININT;
            // ds_p->sprtopclip = screenheightarray;
        }

        if (backsector->ceilingheight <= frontsector->floorheight)
        {
            ds_p->sprbottomclip = negonearray;
            ds_p->bsilheight = MAXINT;
            ds_p->silhouette |= SIL_BOTTOM;
        }

        if (backsector->floorheight >= frontsector->ceilingheight)
        {
            ds_p->sprtopclip = screenheightarray;
            ds_p->tsilheight = MININT;
            ds_p->silhouette |= SIL_TOP;
        }

        worldhigh = backsector->ceilingheight - viewz;
        worldlow = backsector->floorheight - viewz;

        // hack to allow height changes in outdoor areas
        if (frontsector->ceilingpic == skyflatnum
                && backsector->ceilingpic == skyflatnum)
        {
            worldtop = worldhigh;
        }


        if (worldlow != worldbottom
                || backsector->floorpic != frontsector->floorpic
                || backsector->lightlevel != frontsector->lightlevel)
        {
            markfloor = true;
        }
        else
        {
            // same plane on both sides
            markfloor = false;
        }


        if (worldhigh != worldtop
                || backsector->ceilingpic != frontsector->ceilingpic
                || backsector->lightlevel != frontsector->lightlevel)
        {
            markceiling = true;
        }
        else
        {
            // same plane on both sides
            markceiling = false;
        }

        if (backsector->ceilingheight <= frontsector->floorheight
                || backsector->floorheight >= frontsector->ceilingheight)
        {
            // closed door
            markceiling = markfloor = true;
        }


        if (worldhigh < worldtop)
        {
            // top texture
            toptexture = texturetranslation[sidedef->toptexture];
            if (linedef->flags & ML_DONTPEGTOP)
            {
                // top of texture at top
                rw_toptexturemid = worldtop;
            }
            else
            {
                vtop =
                    backsector->ceilingheight
                    + textureheight[sidedef->toptexture];

                // bottom of texture
                rw_toptexturemid = vtop - viewz;
            }
        }
        if (worldlow > worldbottom)
        {
            // bottom texture
            bottomtexture = texturetranslation[sidedef->bottomtexture];

            if (linedef->flags & ML_DONTPEGBOTTOM )
            {
                // bottom of texture at bottom
                // top of texture at top
                rw_bottomtexturemid = worldtop;
            }
            else		// top of texture at top
                rw_bottomtexturemid = worldlow;
        }
        rw_toptexturemid += sidedef->rowoffset;
        rw_bottomtexturemid += sidedef->rowoffset;

        // allocate space for masked texture tables
        if (sidedef->midtexture)
        {
            // masked midtexture
            maskedtexture = true;
            ds_p->maskedtexturecol = maskedtexturecol = lastopening - rw_x;
            lastopening += rw_stopx - rw_x;
        }
    }

    // calculate rw_offset (only needed for textured lines)
    segtextured = midtexture | toptexture | bottomtexture | maskedtexture;

    if (segtextured)
    {
        offsetangle = rw_normalangle-rw_angle1;

        if (offsetangle > ANG180)
            offsetangle = -offsetangle;

        if (offsetangle > ANG90)
            offsetangle = ANG90;

        sineval = finesine[offsetangle >>ANGLETOFINESHIFT];
        rw_offset = FixedMul (hyp, sineval);

        if (rw_normalangle-rw_angle1 < ANG180)
            rw_offset = -rw_offset;

        rw_offset += sidedef->textureoffset + curline->offset;
        rw_centerangle = ANG90 + viewangle - rw_normalangle;

        // calculate light table
        //	use different light tables
        //	for horizontal / vertical / diagonal
        // OPTIMIZE: get rid of LIGHTSEGSHIFT globally
        if (!fixedcolormap)
        {
            lightnum = (frontsector->lightlevel >> LIGHTSEGSHIFT)+extralight;

            if (curline->v1->y == curline->v2->y)
                lightnum--;
            else if (curline->v1->x == curline->v2->x)
                lightnum++;

            if (lightnum < 0)
                walllights = scalelight[0];
            else if (lightnum >= LIGHTLEVELS)
                walllights = scalelight[LIGHTLEVELS-1];
            else
                walllights = scalelight[lightnum];
        }
    }

    // if a floor / ceiling plane is on the wrong side
    //	of the view plane, it is definitely invisible
    //	and doesn't need to be marked.


    if (frontsector->floorheight >= viewz)
    {
        // above view plane
        markfloor = false;
    }

    if (frontsector->ceilingheight <= viewz
            && frontsector->ceilingpic != skyflatnum)
    {
        // below view plane
        markceiling = false;
    }


    // calculate incremental stepping values for texture edges
    worldtop >>= 4;
    worldbottom >>= 4;

    topstep = -FixedMul (rw_scalestep, worldtop);
    topfrac = (centeryfrac>>4) - FixedMul (worldtop, rw_scale);

    bottomstep = -FixedMul (rw_scalestep,worldbottom);
    bottomfrac = (centeryfrac>>4) - FixedMul (worldbottom, rw_scale);

    if (backsector)
    {
        worldhigh >>= 4;
        worldlow >>= 4;

        if (worldhigh < worldtop)
        {
            pixhigh = (centeryfrac>>4) - FixedMul (worldhigh, rw_scale);
            pixhighstep = -FixedMul (rw_scalestep,worldhigh);
        }

        if (worldlow > worldbottom)
        {
            pixlow = (centeryfrac>>4) - FixedMul (worldlow, rw_scale);
            pixlowstep = -FixedMul (rw_scalestep,worldlow);
        }
    }

    // render it
    if (markceiling)
        ceilingplane = R_CheckPlane (ceilingplane, rw_x, rw_stopx-1);

    if (markfloor)
        floorplane = R_CheckPlane (floorplane, rw_x, rw_stopx-1);

    R_RenderSegLoop ();


    // save sprite clipping info
    if ( ((ds_p->silhouette & SIL_TOP) || maskedtexture)
            && !ds_p->sprtopclip)
    {
        memcpy (lastopening, ceilingclip+start, 2*(rw_stopx-start));
        ds_p->sprtopclip = lastopening - start;
        lastopening += rw_stopx - start;
    }

    if ( ((ds_p->silhouette & SIL_BOTTOM) || maskedtexture)
            && !ds_p->sprbottomclip)
    {
        memcpy (lastopening, floorclip+start, 2*(rw_stopx-start));
        ds_p->sprbottomclip = lastopening - start;
        lastopening += rw_stopx - start;
    }

    if (maskedtexture && !(ds_p->silhouette&SIL_TOP))
    {
        ds_p->silhouette |= SIL_TOP;
        ds_p->tsilheight = MININT;
    }
    if (maskedtexture && !(ds_p->silhouette&SIL_BOTTOM))
    {
        ds_p->silhouette |= SIL_BOTTOM;
        ds_p->bsilheight = MAXINT;
    }
    ds_p++;
}

